037 tap destination matching

// Test 310_037: Tap Destination Pattern Matching
// =================================================
// BUG: Tap with destination pattern `* -> target` matches ALL flows,
// not just flows that actually transition to `target`.
//
// This test has:
// - target: the event we want to tap transitions TO
// - other: an event that does NOT transition to target
//
// Expected: tap ONLY fires for flow that calls target
// Actual (bug): tap fires for flow that calls other too

const std = @import("std");
~import "$std/taps"

// Two simple events
~event target {}
| done {}

~event other {}
| done {}

// Procs
~proc target {
    std.debug.print("target called\n", .{});
    return .{ .done = .{} };
}

~proc other {
    std.debug.print("other called\n", .{});
    return .{ .done = .{} };
}

// Logger for tap - void return
~event log {}

~[pure] proc log {
    std.debug.print("TAP: going to target\n", .{});
}

// Tap: observe transitions TO target (not FROM target)
// Pattern `* -> target` means "any source going TO target"
~tap(* -> target)
| Transition _ |> log()

// Flow 1: DOES call target - tap SHOULD fire
~target()
| done _ |> _

// Flow 2: does NOT call target - tap should NOT fire
~other()
| done _ |> _